Electric control device



March 26, 1957 J. SCHULTZ E AL 2,786,898

ELECTRIC CONTROL DEVICE Filed Jan. 19, 1953 3 Sheets-Sheet l gELVER/V ORTO/V ATTORNEY March 26, 1957 H. J. SCHULTZ ET AL 2,786,898

llllllll 19,, 1953 March 26, 1957 'EN TOR SCHULTZ ER/V 0/? row BY am am ATTORNEY HENRY J. MELV United States Patent ELECTRIC CONTROL DEVICE Henry J. Schultz, Hayward, and Melvern Orton, Alameda, Calif.

Application January 19, 1953, Serial No. 331,988 7 Claims. (Cl. 179100.41)

This invention relates to an improved phonograph pickup and to other electric control devices, of the typeemploying a fluid current-modulating medium.

In the type of pickup to which this invention relates, the phonograph needle is mounted on an actuator member or armature which is rotated back and forth across a small arc as the needle moves back and forth laterally in the record groove. The rotative movement of the i210- tuator is used to modulate an electric current that flows between two or more electrodes through an electrolytic fluid conained in cavities or cells in a housing made of insulating material.

A preferred pickup construction div-ides the housing into three serially adjoining cavities, each containing an electrode and liquid. The central cavity is joined to the other cavities by a pair of orifices whose areas are varied by the actuator member in response to the movement of the needle. Each time the orifice changes in size, the electrioal resistance between adjacent chambers changes, varying the current flow and voltage between them. In a pickup having three chambers, a difference in electric potential can be set up across the electrodes in the end chambers, and a varying voltage can be obtained from the electrode in the central chamber. This variation, obtained by varying the areas of the orifices between the central chamber and the other two chambers, causes the voltage on the electrode in the central chamber to increase and decrease relatively to the potential of the other two electrodes, although voltage between these two electrodes re mains constant.

The present invention solves several problems that had beset the above-described type of device. For one thing, it simplifies both the manufacture of the individual components and their assembly into the finished product. Costs are reduced and time saved. Cheaper and less fragile materials can be used, and the dies can be less expensive and easier to reproduce.

One problem related to assembly was that glue tended to get into the orifices and cause trouble. In the present invention, gluing is not always necessary, and if glue or cement is used, it is used at a distance from the orifices themselves, where it cannot possibly get in them and plug them.

Another problem related to assembly was the difficulty of holding the actuator or armature in exactly the right position, under exactly the right amount of pressure. Special straps, dampers, and pads were used heretofore. In the present invention the actuator is molded in place in the exact position and is held by the correct pressure. Moreover the armature may be simpler than heretofore without sacrificing any quality in results. The armature may also be of the invertable type, with two needles, one on each end to take the two major different types of record grooves. A change may then be made simply by inverting the cartridge of this invention.

'Another problem solved by this invention is that of compression set, which occurred when some rubber or synthetic rubber parts were retained under tension at all ice times. The result was a permanent displacement of the parts and a change in the performance characteristics of the unit. This has been solved in the present invention by not exerting pressure on the working parts except during actual operation, when the pressure is constantly changing and is of small magnitude.

Other problems, such as that of providing for the fluid expansion that occurs with changes in temperature, and that of providing housings for securing the cartridge to the tone arm, have also been solved. The solutions to these problems, as well as other objects and advantages of the invention will appear from the following description of a preferred embodiment. Details :are given in accordance with United States Revised Statutes Section 4888 and not with the idea of narrowly limiting the invention as de fined in the appended claims.

In the drawings:

Fig. 1 is an enlarged isometric view of a photograph pickup cartridge embodying the principles of the present invention.

-Fig. 2 is a view in side elevation of the cartridge of Fig. 1, with the outer ends of the actuator or armature broken ofi to conserve space.

Fig. 3 is a view in section taken along the line 3-3 in Fig. 2.

Fig. 4 is a view in section taken along the line 4-4 in Fig. 3.

Fig. 5 is a view in section taken along the line 5-5 in Fig. 3.

Fig. 6 is a view in section taken along the line 6-6 in Fig. 3.

Fig. 7 is a view in section taken along the line 7--7 of Fig. 3.

Fig. 8 is a view in section taken along the line 8--8 in Fig. 3.

Fig. 9 is :a further enlarged view of a portion of Fig. 3.

Fig. 10 is a view in perspective of a frame to which the cartridge may be molded, and by which it may be supported in a tone arm.

Fig. 11 is a view similar to Fig. 10, showing a cartridge, somewhat modified in form from the form shown in Figs. 1-9, molded in place.

Fig. 12 is a View in elevation and partly in section of a tone arm in which another modified form of cartridge, held in a frame has been mounted.

Fig. 13 is a view in perspective of the cartridge shown in Fig. 12.

Brief general description The pickup cartridge 20 shown in Figs. 1-9 includes a housing A that encloses three chambers B, C, and D filled with electrically conductive liquid E. A resilient deformable diaphragm, valve, or membrane F extends down into the central chamber C and controls the communication between the respective chambers and between the respective electrodes G, H, and I contained in the chambers B, C, and D. Electric current flows between the electrodes only by way of two orifices J and K, both of which are varied in area by the member F in accordance with the movement of an armature or actuator L, Whose stem M extends down inside the valve member F and is bonded there.

' Movement of either of two needles N at the outer end of the armature L causes the stem M to twist or partially turn, so as to twist or turn the valve member F, so that first one orifice J is made smaller and the orifice K enlarged, and then the opposite action occurs. When the orifice I is made smaller, the resistance between the electrodes G and H is increased; at the same time the widening of the orifice K decreases the resistance between the electrodes H and I. These changes vary the voltage on the electrode H, which is used as the output voltage of the pickup 2%. When the orifice J is opened and the orifice K is made smaller, the reverse situation exists between the electrodes. In this manner, the shape of the record groove is reproduced in the change of re sistance within the cartridge 20, and the resultant fluctuation of voltage in the center electrode H can be used in conjunction with an amplifier and loud-speaker to give a faithful reproduction of the original sound.

The housing A In this invention the housing A may comprise two parts: one portion 21 may contain and include the three cavities B, C, and D, as well as the deformable valve F, while the other part may be a closure member 22. The closure member 22 may be made from glass, plastic, suitable types of synthetic resins, of synthetic rubber, and may support the three electrodes G, H, and I, so that when the body A is secured together they extend inside the chambers B, C, and D. Terminal connections 23, 24, 25 for the electrodes extend beyond the closure member 22. The member 22 also may be provided with a socket 26 adapted to receive and hold the member 21, either with or without being cemented together. If desired, the closure member 22 may be larger and be provided with continuations of the cavities B, C, and D and with partitions for separating them.

The member 21 is preferably made from very flexible, chemical-resistant, synthetic rubber, and is preferably molded to shape. Its open rear end 27 is preferably flat, to fit snugly against the closure member 22, and its forward end 28 is closed.

The shape of the cavities B, C, and D is not greatly important, but it is convenient for cavities B and D, which carry the current load to be larger than the central cavity C and to terminate at the flat front wall 30. It is also convenient for the cavity C to be round and for the structure to be symmetric. The partition 31 which divides chambers B and C and the partition 32 which divides chambers C and D are integral with the housing A and blend into the partitions 33 and 34 that directly divide the partitions B and D. (See Figs. 4 and 5.)

Not only may the chamber C be smaller cross-sectionally than the chambers B and D. It is also preferably shorter, extending about three-fourths of the way from the open rear end 27 of the housing A to the closed forward end 36 of the cavities B and D. This structure is especially convenient when using the valve member F shown in the drawings.

The valve or diaphragm F The change in size of the orifices I and K and the location of these orifices is controlled by a resilient, flexible diaphragm or valve F that is preferably an integral part of the housing member 21. The valve F is axially in line with the central cavity C and extends into it, its stem 35 extending out from the Wall 30 having a narrow portion 36 and a flared portion 37, to provide a pair of fins or membranes 3%, 39 as shown in Figs. 3 and 9.

In order to assure separation of the chambers B and D and make the current flow through the chamber C, via both orifices I and K, en route between the electrodes G and I, across which the outside potential is placed, the valve F is provided with narrow webs 40, 41 that are preferably integral with the partitions 33, 34. This also means that the movement of the valve F is restrained by the webs 40, 41, and that it is freest to move midway inbetween the webs. This structure has a desirable damping effect on the valve F that prevents the formation of undesirable harmonics and faithfully transmits the transduced energy.

The actuator L The actuator L preferably has a stem M that may be round, rectangular, or otherwise shaped in cross sectlon, and extends down through the axis of the member 21 and into the stem 35 of the valve F, terminating at or adjacent the flared valve portion 37. One or two vertical shanks 42 extend out generally perpendicular to the stem M and are provided at their outer ends with a stylus arm 43 that terminates in the needle point N. The two needle construction shown in the drawings is advisable for getting the best results out of both the standard types of record grooves, but is not an absolute necessity. A singie-needle type of actuator may be used, in which event there will be only one shank 42 and one stylus arm 43. The simplicity of the structure is in either event an important advantage of the armature L used in this invention.

The actuator L is preferably metal, prepared and shaped in advance and then inserted in the mold (not shown) before the member 21 is poured. It is therefore bonded into exactly the correct position in the member 21 and its rotative movement is restrained uniformly and in exactly the correct amount, as predetermined by calculations based on the proportions and compositions of the materials and on the results desired. Instead of consuming several assembly steps, only one step is taken and exact and uniform results are assured.

Movement of either needle N in a record groove will cause both the stem M and valve F to twist or turn, and this will alternately enlarge the orifice I while decreasing the orifice K, and diminish the orifice .I while enlarging the orifice K. The degree and extent of movement will be determined by the resiliency or flexibility of the material from which the housing member A is made, by the cross-sectional area of the valve F, by the thickness and length of the webs 40, 41, and by the amount of rubber covering the portions M and 42 of the armature L. By changes in these parts, practically any desired performance characteristics can be obtained. Perfect fidelity over a wide frequency range or emphasis of some parts of the range may be achieved without the necessity of any additional parts. The compliance of the actuator L, the snubbing or stop action of the actuator, all are provided by a proper proportioning of the parts of the member 21, by its chemical composition, and by the location of the actuator L therein.

Manufacture and assembly Heretofore, a typical pickup of the fluid-modulating type had fourteen separate parts, some of which were preassembled (as during molding), but the final assembly involved putting ten separate pieces together. The cartridge 20 has six separate parts-the actuator L, the body members 21 and 22, and the electrodes 23, 24 and 25. The parts are made separately, but it should be noted that the electrodes are identical; so there are only four kinds of parts. The three electrodes 23, 24, 25 are positioned in the mold (not shown) when the body member 22 is poured. The actuator L is similarly positioned in the other mold (not shown) when the body member 21 is poured. The final assembly is simply putting the body members 21 and 22 together, and all this means is placing the body member 21 in the socket 26. Glue may be placed on the end 27, or a sealant, such as Dow-Cornings silicone grease DC-4 may be used to make sure that the chambers B, C, and D are properly separated, but the application of the glue or grease is a very simple and very rapid operation, and there is no danger of the glue or grease getting into the orifices J and K as there was in the prior art.

Operation An electric potential is placed across the outer electrodes G and I, and the output from the electrode H is drawn off to a loud speaker system or amplifier. The proper needle N is placed on the record and follows its grooves. As a result the stem M tends to rotate back and forth, carrying the valve F with it, thereby and alternately enlarging the orifice I while diminishing the orifice K and vice versa. As a result, the voltage output of the electrodes H varies, transmitting the recorded sound in the record groove to the reproduction system where it is amplified, if necessary, and converted into sound energy.

Instead of being used as a phonograph pickup, the cartridge 20 may be used for a microphone or other type of transducer.

It will be obvious from the above that any gluing done in assembly is done remote from the orifices J and K, that the armature L is held in place directly by the member 21, of which the valve F is usually an integral molded part, that no additional parts are needed to regulate the compliance or range of action of the armature L, and that there is no resultant change in fluid pressure brought about by the valving action. Even if there were, the resilience of the housing member 21 would accommodate it, as it accommodates changes in fluid pressure caused by temperature changes.

Installing the cartridge in a tone arm The cartridge 20 may be held directly in a tone arm by a simple clip (not shown) which may be mounted for rapid inversion, in order to place one needle in use instead of the other. This structure is conventional, is well known, and is satisfactory.

However, the nature of the present invention renders it capable of use with frames of a novel type that bring some additional advantages and simplicityv The low cost of the entire device makes it possible to throw the whole thing away when the point N becomes worn, instead of changing the point.

For example, the frame 50, shown in Figs. and 11 may be used. The frame 50 may be metal, or may be some other material, such as a suitable plastic. It is open on five sides, so that the cartridge is still free to expand under changes of fluid pressure. Its front face 51 is provided with an opening 52, through which a portion 53 of the rubber body 21 and the actuator L project. Slots 54, 55 are also provided.

The frame 50 is placed in the mold (not shown) when the body member 21 is molded, and becomes bonded to it, as shown in Fig. 11. All the tone arm (not shown) needs to have is a pair of vertical prongs or bolts or other members (not shown) that engage the slots 54, 55 and keep the cartridge from falling out. Inversion is accompilshed by pulling out the cartridge, turning it over, and re-inserting it. The frame 50 may be rectangular as shown, resulting in a slight, inconsequential modification in shape of the cartridge from that shown in Figs. 1-9, or the frame 50 may be rounded, oval, or some other shape.

The frame 69, illustrated in Figs. 12 and 13 may be simply a perforated metal strip, bent to shape and with the rubber body 61 bonded to it by means of the perforations 62. In this instance holes or sockets 63, 64 are molded directly in the rubber body 61, which in most particulars is like the body 21. The holes 63, 64 may be inclined as shown, and the prongs 65 on the tone arm 66 may also be inclined. In this instance the pickup 61 has only one needle N and is not invertable, but obviously it may be made invertable, with two needles.

To those skilled in the art to which this invention relates, many changes in construction and widely difiering embodiments and applications of the invention will suggest themselves without departing from the spirit and scope of the invention. The disclosures and the description herein are purely illustrative and are not intended to be in any sense limiting. For example, the rear body member 22 need not be wider than the front body member 21, nor need the member 22 be provided with a socket 26. Instead, the rear ends of the partitions 31 and 32 may be stopped short of the rear end 27, and a rigid rear body member generally like the member 21 but narrower than the front body member 22 may be pushed into the member 22 to close the chambers. In this case, the rear member may be a little wider than the interior space inside the member 21, so that the member 21 is stretched out somewhat, thereby tightening the connection.

Also, the actuator L may be designed to be replaceable, so that the whole actuator assembly is removable, and a new one may be inserted in the body A when the points N wear out.

In any event, it will be noted that the orifice structure here provided is unaffected by pressure changes in the fluid, so that uniformly good results are obtained.

We claim:

1. An electric control device, including in combination: a hollow body having a major portion thereof composed of a synthetic rubber; partitions in and integral with said body dividing it into at least three chambers with passages connecting each chamber to at least one other chamber; a synthetic rubber valve member integral with said synthetic rubber portion of said body, projecting from said body and extending inside one chamber that adjoins two other chambers, said valve member cooperating with said partitions to provide a pair of variable-area orifices connecting said one chamberto said two other chambers, the size of said orifices being varied by torsion applied to said valve member; an electrode in each said chamber and extending outside said body; electrolytic fluid filling said chambers; and an actuator having a portion extending inside said body and adapted for applying torsion on said valve member and a portion extending outside said body responsive to an externally applied force.

2. An electric control device, including in combination: a hollow, resiliently deformable .body divided by partitions into three chambers, one of which lies centrally between the other two outer ones; a valve member integral with said body, with a projecting portion separating the two outer chambers from each other, and having an enlarged projecting portion in between and spaced from the partitions to provide therebetween a pair of orifices connecting the central chamber, respectively, with each of the two outer chambers, the areas of the orifices being varied by the movement of said enlarged portion; fluid filling said chambers; electrodes extending through said body into each of the three chambers; and an actuator member having a portion extending inside said body and valve member and into said enlarged portion and adapted for exerting force on said enlarged portion, said actuator extending outside said body and being responsive to an externally applied force.

3. An electric control device, including in combination: a hollow, resiliently deformable body divided by partitions into three chambers, one of which lies centrally between the other two outer ones; a valve member integral with said body and projecting therefrom into the central chamber, separating the two outer chambers from each other, and having an enlarged portion spaced from the partitions and in between them to provide a pair of orifices connecting the central chamber, respectively, with each of the two outer chambers, the areas of the orifices being varied by the movement of said enlarged portion; fluid filling said chambers; electrodes extending through said body into each of the three chambers; and an actuator member partially embedded in said body and having a stem extending inside said valve member to a point adjacent said enlarged portion and adapted for exerting force on said enlarged portion, said actuator extending outside said body and being responsive to an externally applied force.

4. An electric control device, including in combination: a hollow body divided by partitions into three chambers, one of which lies centrally between the other two outer ones, said body being constructed fromtwo members assembled together, one said body member be ing made from a resilient insulating material, recessed from, one end to provide said chambers unrecessed portions providing the partitions, and having at its other end an intergral valve member extending toward the first mentioned end and separating the two outer chambers from each other, said valve having a distortable mom brane spaced from the partitions at a point centrally in between them to provide in the clearance space between said membrane and said partitions a pair of orifices connecting the central chamber, respectively, with each of the two outer chambers, the areas of the orifices being varied by the movement of said membrane; the second said body member closing the open end of the first said body member and being made from an insulating material; fluid filling said chambers; electrodes extending through said second body member into each of the three chambers; and an actuator member having a stem bonded inside said valve member and adapted for exerting force on said membrane, said actuator member extending outside said first body member and being responsive to an externally applied force.

5. A phonographic pickup, including in combination: a rigid metal perforate frame; a hollow body bonded to said frame divided by partitions into three chambers, one of which lies centrally between the other two outer once, said body being constructed from two members as sembled together, one said member being made from a resilient insulating material, recessed at one end to provide said chambers and at its other end having an integral valve member projecting toward said first-mentioned end and separating the two outer chambers from each other, said valve member having a distortablc membrane spaced in between the partitions to provide a pair of orifices connecting the central chamber, respectively, with each of the two outer chambers, the areas of the orifices being varied by the movement of said membrane; the second said body member closing the open end of the first said body member and being made from an insulating material; electrodes extending through said sec ond body member, one into each of the three chambers; fiuid filling said chambers; an actuator having a portion embedded in the wall of said body near said valve, a stem portion thereof extending axially inside said valve member adjacent said membrane and fully embedded therein, for exerting force on said membrane to vary orifices, said actuator having a portion extending outside said body; and a phonograph needle on the outer end of said actuator.

6. The pickup of claim 5 in which said frame is rectanguiar with five open faces and one face partially open and partially closed and with mounting sockets in said partially closed face.

7. The pickup of claim 5 in which said frame comprises a perforated bendable strip that is bonded through said perforations with said body, said strip being shaped to bound a portion of said body.

References Cited in the file of this patent UNETED STATES PATENTS 203,018 Edison Apr. 30, 1878 2,60l,l26 Palo ct al. June 17, 1952 2,648,726 Warner Aug. 11, 1953 2,703,822 Warner Mar. 8, 1955 POREEGN PATENTS 135,157 Great Britain Nov. 13, 1919 

